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Learning attribute grammars for movement primitive sequencing

Lioutikov, Rudolf ; Maeda, Guilherme ; Veiga, Filipe ; Kersting, Kristian ; Peters, Jan (2023)
Learning attribute grammars for movement primitive sequencing.
In: The International Journal of Robotics Research, 2020, 39 (1)
doi: 10.26083/tuprints-00016980
Article, Secondary publication, Publisher's Version

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Item Type: Article
Type of entry: Secondary publication
Title: Learning attribute grammars for movement primitive sequencing
Language: English
Date: 28 November 2023
Place of Publication: Darmstadt
Year of primary publication: January 2020
Place of primary publication: Thousand Oaks, California, USA
Publisher: SAGE Publications
Journal or Publication Title: The International Journal of Robotics Research
Volume of the journal: 39
Issue Number: 1
DOI: 10.26083/tuprints-00016980
Corresponding Links:
Origin: Secondary publication DeepGreen

Movement primitives are a well studied and widely applied concept in modern robotics. However, composing primitives out of an existing library has shown to be a challenging problem. We propose the use of probabilistic context-free grammars to sequence a series of primitives to generate complex robot policies from a given library of primitives. The rule-based nature of formal grammars allows an intuitive encoding of hierarchically structured tasks. This hierarchical concept strongly connects with the way robot policies can be learned, organized, and re-used. However, the induction of context-free grammars has proven to be a complicated and yet unsolved challenge. We exploit the physical nature of robot movement primitives to restrict and efficiently search the grammar space. The grammar is learned by applying a Markov chain Monte Carlo optimization over the posteriors of the grammars given the observations. The proposal distribution is defined as a mixture over the probabilities of the operators connecting the search space. Moreover, we present an approach for the categorization of probabilistic movement primitives and discuss how the connectibility of two primitives can be determined. These characteristics in combination with restrictions to the operators guarantee continuous sequences while reducing the grammar space. In addition, a set of attributes and conditions is introduced that augments probabilistic context-free grammars in order to solve primitive sequencing tasks with the capability to adapt single primitives within the sequence. The method was validated on tasks that require the generation of complex sequences consisting of simple movement primitives using a seven-degree-of-freedom lightweight robotic arm.

Uncontrolled Keywords: Movement primitives, movement primitive sequencing, probabilistic context-free grammar, attribute grammar, grammar induction, human-robot interaction
Status: Publisher's Version
URN: urn:nbn:de:tuda-tuprints-169802
Classification DDC: 000 Generalities, computers, information > 004 Computer science
Divisions: 20 Department of Computer Science > Intelligent Autonomous Systems
Zentrale Einrichtungen > Centre for Cognitive Science (CCS)
Date Deposited: 28 Nov 2023 10:38
Last Modified: 01 Dec 2023 10:43
SWORD Depositor: Deep Green
URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/16980
PPN: 513579567
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